1. Field of the Invention
The invention relates to a coupling for a light-conducting fiber, including a metal body, in which is disposed a first device for holding an end piece of a light conducting fiber, a housing for an opto-electronic transmitting element, and a second device for holding the opto-electronic transmitting element in its housing such that an exit opening of the element is opposite an end face of the fiber.
2. Description of the Prior Art
Couplings of the abovenoted type have been known for some time from the technology of optical data transmission. The opto-electronic transmitting element used has an optical axis extending in a direction which is the preferred direction for emitting the light signals. The light-conducting fiber, having an end face into which the optical signals are to be coupled, also has its own optical axis which is fixed by a device in the coupling. For protecting the active part of the opto-electronic transmitting element, the latter is built into a closed housing into which an exit opening for the light signals is recessed, mostly at the front.
Because of the production conditions, displacements of up to 0.5 mm usually occur in the opto-electronic transmitting elements in the housing between the optical axis and the housing axis, which displacements must be taken into consideration when installing the completed element into a coupling. In order to achieve optimum coupling of light into the light-conducting fiber, it is essential, therefore, to align the transmitting element in the coupling with reference to the optical axis of the light-conducting fiber and, following that, fix the transmitting element in the aligned position.
Usually, this is done by centering the transmitting element in its housing in the holding fixture of the coupling, which has sufficient clearance both in the axial and in the radial direction, having regard to optimum coupling and then potting it with an adhesive.
In a coupling produced in this manner, the housing of the transmitting element is joined to the coupling body only via the adhesive or at the most via gas-filled cavities created during the potting. This adds to the, in most cases desired, electrical insulation of the transmitting element with respect to the coupling body, and to a thermal insulation which impedes dissipation of the heat, produced in the transmitting element, to the metallic coupling body. This structure can lead to thermal overloading of the transmitting element, especially under extreme environmental conditions. Since thermal overloading, however, considerably reduces the life of the transmitting element and thus causes outages in the operation of whole transmission sections, ways must be found for reducing this risk factor in optical data transmission. Since the couplings are used in greater numbers in a transmission network, the required improvements must also not have any significant effect on the production costs.